spankrjs's Biloxi, MS '83 Scrambler

spankrjs

Scrambler Junkie
LIFETIME
CJ-8.com Member
City
Biloxi
State
MS
One minor "hiccup" I have experienced with the Mopar MPI and the addition of air conditioning:

The Mopar MPI computer does NOT support AC. On a factory 4.0 computer, when the AC is turned on, the computer will get a signal to slightly idle up the engine. The MPI computer does not have this function. I had some minor "stalling" type issues last year when it was hot with the AC on, talked to Hesco about it, and they recommended this:

IMG_20190414_112401509.jpg

Basically, I drilled a small "bleed hole" through the throttle plate. In this way, the engine is sucking in a bit more air then what the IAC will flow at idle. IIRC, with the engine running, I covered up the IAC slot in the throttle body with a piece of stiff paper, which kind of chokes the engine down. I kept enlarging the hole in the throttle plate, with the IAC slot covered up, until the engine maintained a base idle of 725-750 RPM.

That is all fine an dandy, mostly. With the hole plugged up, base idle speed is good, no AC:

IMG_20190414_112409919_HDR.jpg

With the hole unplugged, no AC, the idle is a bit higher then I like, but OK:

IMG_20190414_112437306_HDR.jpg

And with the hole unplugged, AC ON:

IMG_20190414_112445963_HDR.jpg

As you can see, when the AC compressor engages, it puts a load on the motor. So, kind of a compromise. A slightly high base idle with the AC OFF, correct idle with the AC on. I was surprised how much the compressor will bog down the engine.

On a stock Carter BBD equipped CJ, with AC, the computer will receive a signal from the AC compressor, which then tells the Sol-Vac to kick up the idle.

I could "plug" the hole in cold months, unplug it in AC months, but I just live with it. Not a big deal, and I am more then happy to live with the slightly higher idle AND have working AC :twocents:

Drove this one to work today, drove around all day with the AC on, no problems:

IMG_20190416_114957929.jpg

I need to check out a few more things, then this one should be ready as a "stand-by" for the National Event IF the Red Scrambler has any problems.

That's it for now :wave:
 

Jeep Addict

Scrambler Junkie
LIFETIME
CJ-8.com Member
City
Baton Rouge
State
La
Wasn’t sure what was up with the previous wheels either. This set looks much more better. I would opt out the chrome hinges too if possible. If it were mine. Great job spankx
 

spankrjs

Scrambler Junkie
LIFETIME
CJ-8.com Member
City
Biloxi
State
MS
Wasn’t sure what was up with the previous wheels either. This set looks much more better. I would opt out the chrome hinges too if possible. If it were mine. Great job spankx
The previous owner gave me all of the OEM hinges, repainting them to match would be a PIA, so I just added more chrome :shrug:
 

spankrjs

Scrambler Junkie
LIFETIME
CJ-8.com Member
City
Biloxi
State
MS
Since the weather is nice and hot, I started having problems with this one again, vapor lock :banghead:

Quick recap:

In September of 2017 I finished swapping in the rebuilt engine with the Mopar MPI.

September 2017 - March 2018 is cooler weather, no problems.

March -August 2018 - went through chemo, and recovery from that, so I did not drive the Scrambler hardly at all.

Added air Conditioning in August of 2018. Very hot outside. I started having intermittent vapor locking problems.

Once it cooled down in 2018, till April 2019, no vapor locking problems. But, cooler weather.

Now, with it 95 degrees.90% humidity, I can drive about 20 minutes, then vapor lock :banghead:


When I put the engine/fuel injection in the Scrambler, I did every preventive measure I could think of to prevent vapor lock:

1) in tank fuel pump
2) all fuel lines run down passenger side frame rail, exhaust on driver side
3) single line fuel rail (pressure regulator in the rear near the tank, no hot fuel returning to tank)

On my red Scrambler, which now has a 4.0, but had a 4.2, it runs the same Mopar MPI, but with the earlier supply and return lines on the fuel rail, pressure regulator on the rail. I have had maybe three issues with vapor issues on this system. And, I have the fuel supply/return lines running down the driver side frame rail, next to the exhaust. I plan on moving the two lines over to the passenger side frame rail, still haven't done that. Anyway, I wonder if this earlier "return line on the fuel rail" set up is better at fighting the vapor lock :shrug::twocents:

Anyway, back to the green Scrambler. I will have to drive it again, without the AC on, to see if that makes a difference. I think the AC does add to the under hood heat, so it causes the vapor lock to come on sooner.

Anyway, I drove the Jeep 10 minutes to the gas station this past Saturday, no AC on. It was low on gas. It had older non-ethanol 87 octane in it. Took 13.5 gallons to fill the 15 gallon tank. I filled it up with 93 octane regular gas. Started up fine, turned the AC on. It was close to 100 degrees out, 90%+ humidity. Drove it less then 5 minutes to NAPA, switched the AC OFF BEFORE turning the Jeep off, it started to stumble/missfire. Turned it off, went inside for 15 minutes. Came back out, started it up, it was miss firing very bad. Turned it off. Took the cap off the schrader valve, got some rags, depressed the valve, drained all the air/hot fuel out of the rail. Turned key on three times to fill up the fuel rail/pressurize it, Scrambler started up fine, drove home fine, with the AC on. Turned the AC off in the yard, turned Jeep off. Restarted it, same thing, miss firing bad. Parked it.

Drove the Jeep yesterday afternoon. About the same outside temperature. No AC. Drove it the same route I took Saturday, got it back home, no issues. Turned it off, restarted it in less then 5 minutes, no problems.

So, drove it again, this time with the AC on. Mixed city stop and go traffic, some highway driving. Only once, stopped at a red light and idling, I felt it briefly stumble for a second or two. It cleared up. No other noticeable issues. Drove fine. Drove it for 45 minutes. When I got in the yard, I turned the AC off, Jeep still running. I had the scan tool plugged in the whole time. I checked for trouble codes, had one: IIRC it was a Code 51, "running lean". I could not clear the code with the engine running, so I turned the Jeep off. Turned key on, cleared code, restarted the Jeep, miss fire city. I hooked up a fuel pressure gauge to the rail, 60 psi, like it normally shows.

So, turned the Scrambler off, and carefully poured two cups of water on the fuel rail/injectors. The water instantly boiled off. Started the Jeep up, still stumbling. So, with the fuel pressure gauge still hooked up, and showing 60 psi, I drained the pressure/fuel out of the rail with the gauge. The fuel that came out was very hot, it was actually percolating in the plastic drain cup!! Some air came out, too. The fuel pressure gauges brass block, where the pressure release switch is located, was too hot to touch with my bare fingers, I had to use a glove.

So, drained the fuel rail, turned key on three times to refill/pressurize the rail, then started it. It fired right up, ran perfect.

So, I know what my problem is - vapor lock at the rail/injectors. But, how can I prevent it :shrug:

Other notes, since I had the scan tool plugged in:

1) engine temp at the thermostat housing is 203 degrees, AC On, just a few degrees higher then with the AC Off
2) I am running a 195 degree thermostat
3) stock exhaust manifold, stock 4.0 intake
4) engine is stock rebuild, just a 40 thousandths over bore
5) IAC counts with AC off is zero at idle (I drilled a bypass hole in the throttle plate), with AC on it is around 2-3 at idle
6) the O2 goes "Rich, Center, Lean" at first, BUT after awhile, it stays stuck on "Center"
7) only one trouble code, the "51 Running Lean" (makes sense because it is vapor locking an starving for fuel)
8) fuel pressure is a constant 60 psi at the rail, even when vapor locked (this is about 10 psi higher then spec)
9) the air charge temp gets as high as 140 degrees (pulling intake air from under the hood)

I have no liquid fuel leaks that I can find. I checked the under hood clamps/connections again, none were loose. I need to check the connections back at the tank. I have no "liquid" leaks, but I wonder if something is loose and causing it to "suck in" air, contributing to this issue?

I plan on checking all the connection first.

I also have one of those D.E.I. Fuel Rail insulation kits. I purchased it last August when I first had the issue, might be worth installing. Right now, I do not have any heat shielding at the rail/injector/manifold.

The two 2005 Wranglers I have/had, would briefly exhibit this same issue, only with the current high temps/AC on.

My white 2005 Rubicon that I sold would sometime shudder when idling at a red light, after sustained high speed driving, or on a hot restart. Only sometimes, and very briefly, never caused a check engine light.

My red 2005 LJ Rubicon will do the same as the white one at red lights, and sometimes on a hot restart. This one actually got a check engine light once from it, IIRC "cylinder #3 miss fire". After driving two hours on the interstate at 80 mph, 95+ degrees outside, I turned the Jeep off. Restarted 10 minute later, big time shudder/miss fire. It cleared up after a minute, but caused the check engine light to turn on.

The two Wranglers have an intake manifold heat shield, nothing else. And, they both have those two pre-cats under the hood, which I am sure makes it extra toasty under the hood. The LJ also has under hood insulation!!!!!!!!!!!

Anyway, I will check for loose connections first, then try the heat shield stuff, since I already have it.

Any other suggestions, besides moving :rotfl:
 

bigwalton

Picture cravin' AK Postal nut
Staff member
SOA Member
City
Dexter
State
MI
#1 humans shouldn't be living where this kind of thing is a problem, so yes, move!

#2 I could see the non-return setup actually being more problematic. Circulating fuel may send heated fuel back to the tank, but the tank is still a big reservoir of cooler fuel, so sending a larger volume constantly through the rail doesn't let it sit in there and means it's constantly removing heat from the rail instead of it just heat soaking with the smaller amount that's going through the injectors.

#3 I'd definitely do the DEI heat shield kit. I put one on and added slits to the injector holes so I didn't have to remove the fuel rail. Should have come that way from them IMO. I don't like messing with injector o-rings unless absolutely necessary.

#4 have you put a clothespin on the fuel rail? @MrBeep swears by this fix!!!
 

spankrjs

Scrambler Junkie
LIFETIME
CJ-8.com Member
City
Biloxi
State
MS
#1 humans shouldn't be living where this kind of thing is a problem, so yes, move!

#2 I could see the non-return setup actually being more problematic. Circulating fuel may send heated fuel back to the tank, but the tank is still a big reservoir of cooler fuel, so sending a larger volume constantly through the rail doesn't let it sit in there and means it's constantly removing heat from the rail instead of it just heat soaking with the smaller amount that's going through the injectors.

#3 I'd definitely do the DEI heat shield kit. I put one on and added slits to the injector holes so I didn't have to remove the fuel rail. Should have come that way from them IMO. I don't like messing with injector o-rings unless absolutely necessary.

#4 have you put a clothespin on the fuel rail? @MrBeep swears by this fix!!!
#1) But our winters are so nice :rotfl:

#2) I agree about the return line being better

#3) I'll slap it on since I have it, can't hurt

#4) I was actually looking at some in the garage yesterday!!!!!!!!! I have heard about it..................
 

Belizeit

CJ-8 Member
CJ-8.com Member
City
River Ridge
State
La
The way you discribe it, that fuel is getting extremely hot, I'm trying to figure out right now how to get cooler intake air to the engine.
 

ag4ever

Average Nut
LIFETIME
CJ-8.com Member
City
Richmond
State
TX
Where is the heat that is going into the fuel line coming from? If you isolate that you should solve the issue.

Most modern cars have much less airflow and higher under hood temperatures, so this should be fixable.

If you have the pump in the tank, then you don’t have any opportunity for air to be sucked in, the fuel line is all under pressure. So, I doubt that is the problem, especially since you are seeing 60 psi.

I would focus on line routing to be sure it is not touching the engine, and if it is isolate it with non metallic clamps. Also, the heat shield should do wonders.

As a last resort, convert it to a return line system, let the tank be a heat sink and dissipate any excess heat. But, again, most modern cars use a dead head fuel line, so this should not be required.
 

spankrjs

Scrambler Junkie
LIFETIME
CJ-8.com Member
City
Biloxi
State
MS
Where is the heat that is going into the fuel line coming from? If you isolate that you should solve the issue.

Most modern cars have much less airflow and higher under hood temperatures, so this should be fixable.

If you have the pump in the tank, then you don’t have any opportunity for air to be sucked in, the fuel line is all under pressure. So, I doubt that is the problem, especially since you are seeing 60 psi.

I would focus on line routing to be sure it is not touching the engine, and if it is isolate it with non metallic clamps. Also, the heat shield should do wonders.

As a last resort, convert it to a return line system, let the tank be a heat sink and dissipate any excess heat. But, again, most modern cars use a dead head fuel line, so this should not be required.
The heat going into the fuel line is from the engine/exhaust, basically, just high under hood heat coupled with high outside temperatures/humidity levels.

On the fuel lines, I was super OCD about the routing, since I have had problems with vapor lock before. The fuel line is on the passenger side, exhaust on the driver side. The fuel line wraps under the oil pan to the driver side, where it ties onto the fuel rail. I used a YJ stainless steel "under oil pan line" to cross over from the passenger side to the driver side. It does not come close to the engine, it is spaced down about 1"-1.5", and the line from it to the fuel rail does not come close tot he exhaust.

I am hoping the insulation helps.

One other potential issue - I have 60psi at the rail, it should only be 50psi. Not sure if this 10psi extra contributes to the problem, I doubt it, you would think the higher the pressure the less chance to vapor lock. BUT, the 10psi extra could be causing the injector to not function correctly, causing a lean condition, causing excessive combustion chamber temperatures???
 

bigwalton

Picture cravin' AK Postal nut
Staff member
SOA Member
City
Dexter
State
MI
One other potential issue - I have 60psi at the rail, it should only be 50psi. Not sure if this 10psi extra contributes to the problem, I doubt it, you would think the higher the pressure the less chance to vapor lock. BUT, the 10psi extra could be causing the injector to not function correctly, causing a lean condition, causing excessive combustion chamber temperatures???
Interesting thought. I was thinking that the extra pressure would be helping you but maybe you’re onto something.
 

spankrjs

Scrambler Junkie
LIFETIME
CJ-8.com Member
City
Biloxi
State
MS
I had bought this DEI fuel rail insulation kit awhile back, figured I should install it, see it it helps any:

https://designengineering.com/jeep-97-04-fuel-rail-injector-cover-kit/

It is for a 97-2004 4.0. I have a 258 with a 98 style intake manifold, surprisingly, it fit!!! More on that later.

Pictures of the kit:

IMG_20190709_174529489.jpg

IMG_20190709_174537870_HDR.jpg

And the contents: intake manifold shield, fuel rail wrap, injector wraps, new injector o-rings, instructions, and stickers!!!!!!

IMG_20190709_174627371_HDR.jpg

This is what it currently looks like, no insulation at all.

IMG_20190709_174748911.jpg

One interesting note: these injectors, and the injectors on my red Scrambler (95 style return fuel rail) are fat metal. I am pretty sure the injectors on my LJ are composite. I wonder if the switch from metal to composite injectors helps decrease vapor lock?

IMG_20190709_174754967.jpg

IMG_20190709_174812140.jpg

You can see in the above pictures, on an inline six, the intake/injectors are directly above the exhaust manifold.


First step, I purged the fuel rail. I used my pressure tester, which has a release valve/drain hose, to accomplish this.

IMG_20190709_175137969.jpg

IMG_20190709_175142182.jpg

Since the Jeep sat over 24 hours, there was no fuel/pressure in the line. On a stock YJ/Cherokee there would still be pressure. Those vehicles have a check valve in the fuel system to keep pressure at the rail. I am using an after market in tank pump, and a stock 98 Grand Cherokee filter/regulator, that does not have this feature.

Anyway, just make sure the rail is not pressurized before pulling the fuel supply line off!!!

I am using an aftermarket quick connect fitting at the fuel rail. It comes off like a factory connect, you have to use a special little tool:

IMG_20190709_175818316.jpg

Basically, the round part of the tool is forced into the connector, spreading the prongs out, allowing it to slide over/off the metal fuel line.

IMG_20190709_175827317.jpg
 

spankrjs

Scrambler Junkie
LIFETIME
CJ-8.com Member
City
Biloxi
State
MS
I have the fancy aluminum tools, but the cheap plastic tool works better LOL.

IMG_20190709_175844230.jpg

Next, I remove the bolts that hold on the throttle cable bracket, and removed the throttle cable. I am using a throttle body spacer (not for performance, but to raise the throttle body up higher so the intake hose would clear the valve cover), so there are spacers underneath the bracket that have to come out, too. Three bolts, one cable, pretty simple.

IMG_20190709_180123781.jpg

Next, I removed the metal clips from each injector. I pushed them off with my fingers. Be careful, they can go flying off if you are not careful, i speak from experience LOL.

IMG_20190709_180652420.jpg

IMG_20190709_180916119.jpg

I threw the intake bracket on top of the valve cover, i also removed the air intake hose out of the way, clearing the way to make it easier to pull the fuel rail.

IMG_20190709_180924243.jpg

The fuel rail is held to the intake with four bolts, I removed them next.

IMG_20190709_181117835.jpg

I unplugged the sensor wires from the throttle body, moved them out of the way. No sense labeling them, each one has a different sized plug, no way to mix them up.

IMG_20190709_181421116.jpg

IMG_20190709_181416394.jpg

Next, I pulled off the injector plugs, Mine were already labeled from Hesco. I would definitely label these to avoid mixing them up.

IMG_20190709_181436393.jpg

Next, I pulled the bog plastic wire retainer thing off the head studs. Be careful with this, it is easy to crack, I kind of rolled it downward, then up, came off pretty easy.

IMG_20190709_181909069.jpg
 

spankrjs

Scrambler Junkie
LIFETIME
CJ-8.com Member
City
Biloxi
State
MS
Next, I gently pulled off the fuel rail. This is a PIA. It is pretty hard to pull it off, takes some force, but you have to be careful not to bend it. too. I rocked it back and forth while pulling upward, and it came off. Five of the six injectors came off with it, one stayed in the intake.

IMG_20190709_182631073.jpg

IMG_20190709_182657681.jpg

One of the injectors had some light corrosion/gunk on the end, the others were all clean.

IMG_20190709_182717916.jpg

IMG_20190709_182728161.jpg

This heat shield goes on first.

IMG_20190709_183555869.jpg

It is made to his a 4.0 head, but it fit fine on my 258 head, with just minor trimming to the back sides of each head stud hole.

IMG_20190709_183917712.jpg

My 258 uses two head studs, and a bolt. I am assuming the 4.0's use studs at all three locations? Regardless, it fits on fine.

I also had to trim the hole where one of the throttle cable bracket bolts go.

IMG_20190709_183922305.jpg

I used my Craftsman cutters to cleanly cut the material off the back sides of the three head stud holes, used a utility knife to enlarge the throttle cable bracket hole, worked perfectly.

IMG_20190709_184537027_HDR.jpg

In the above picture, you can see one of the spacers that came with my throttle body spacer kit. The kit came with three spacers to lift the throttle cable bracket up evenly with the throttle body. If you do not have a spacer, you will probably not have to enlarge this hole.

Also, in the above picture, where the screw driver is pointing - this shield came damaged in the package. The thin part was very floppy. I wrapped some aluminum heat shiel tape around this are to reinforce it, worked perfectly.

Heat shield on, fit perfect.

IMG_20190709_184928669.jpg

Plastic wire retainer slid on next. It pins the heat shield in place.

IMG_20190709_185028114.jpg
 
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